Should rather than Must

A UID *should* rather than *must* be a URL. The UID microformat will ordinarily be a URL, but it should be flexible enough to allow it to contain non-network resolvable URIs.

UID + URL -> permalink?

Can you infer that if something is a URL and a UID that it is also a permalink? It seems so. I can't think of any semantic of "permalink" that isn't covered by the union of the semantics of URL and UID.

abbr pattern

Proposals

Just use UID from hCard

Tantek proposed that we see if we can reuse uid from hCard, similar to how we have reused geo and adr from hCard.

create a URI microformat

Xiaoming proposed leaving UID intact in hcalendar and hcard, because whatever written in rfc2426/rfc2445 and their examples cannot be easily changed, and they seem to work well with hcalendar/hcard. Instead a new "URI" microformat should be established for the purpose of indicating something *is* an identifier in general.In this case you can easily reference URI RFC and no further elaboration about persistence/resovlable/uniqueness, because these issues are addressed by various URI specifications.